FMRI signal source analysis using diffusion-weighted spiral-in acquisition

The Novel Angiotensin-(1-7) Analog, A-1317, Improves Insulin Resistance by Restoring Pancreatic β-Cell Functionality in Rats With Metabolic Syndrome

In previous studies we have shown that oral Ang-(1-7) has a beneficial therapeutic effect on cardiometabolic disturbances present in metabolic syndrome (MetS). Based on the fact that Ang-(1-7) acts through release of nitric oxide (NO), a new peptide, A-1317 was engineered adding the amino acid L-Arginine, the NO precursor, to the N-terminal portion of the Ang-(1-7). Therefore, in a single molecule the substrate and the activator of NO are combined. In the present study, we evaluated the effect of A-1317 oral treatment on liver-glucose metabolism in MetS induced by high fat (HF) diet in rats. Rats were subjected to control (AIN-93M, CT) or HF diets for 15 weeks to induce MetS and treated with A-1317, Ang-(1-7) included into hydroxypropyl-β-cyclodextrin (HPβCD) or empty HPβCD (E), in the last 7 weeks. At the end of 15 weeks, hemodynamic, biometric, and biochemical parameters, redox process, and qRT-PCR gene expression of NO synthase and RAS components were evaluated in the liver. HF/E rats increased body mass gain, adiposity index, despite the reduction in food intake, increased plasma leptin, total cholesterol, triglycerides, ALT, fasting blood glucose, OGTT and insulin, HOMA-IR and MAP and HR. Furthermore, the MetS rats presented increased in liver angiotensinogen, AT1R, ACE mRNA gene expression and concentration of MDA and carbonylated protein. Both Ang-(1-7) and A-1317 oral treatment in MetS rats reverted most of these alterations. However, A-1317 was more efficient in reducing body mass gain, ALT, AST, total cholesterol, insulin, fasting blood glucose, ameliorating β cell capacity by increasing HOMA-β and QUICKI, whereas Ang-(1-7) reduced HOMA-β and QUICKI. In addition, Ang-(1-7) increased Mas and AKT liver mRNA gene expression, while A-1317 increased both Mas and MRGD and AMPK liver mRNA gene expression, suggesting a distinct pathway of action of Ang-(1-7) and A-1317 in MetS rats. Taken together, our data showed that treatment with A-1317 was able to ameliorate MetS disorders and suggested that this effect was mainly via MRGD via activation of AMPK and increasing β cell function.

Spiral imaging in fMRI

T2*-weighted Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) requires efficient acquisition methods in order to fully sample the brain in a several second time period. The most widely used approach is Echo Planar Imaging (EPI), which utilizes a Cartesian trajectory to cover k-space. This trajectory is subject to ghosts from off-resonance and gradient imperfections and is intrinsically sensitive to cardiac-induced pulsatile motion from substantial first- and higher order moments of the gradient waveform near the k-space origin. In addition, only the readout direction gradient contributes significant energy to the trajectory. By contrast, the spiral method samples k-space with an Archimedean or similar trajectory that begins at the k-space center and spirals to the edge (spiral-out), or its reverse, ending at the origin (spiral-in). Spiral methods have reduced sensitivity to motion, shorter readout times, improved signal recovery in most frontal and parietal brain regions, and exhibit blurring artifacts instead of ghosts or geometric distortion. Methods combining spiral-in and spiral-out trajectories have further advantages in terms of diminished susceptibility-induced signal dropout and increased BOLD signal. In measurements of temporal signal to noise ratio measured in 8 subjects, spiral-in/out exhibited significant increases over EPI in voxel volumes recovered in frontal and whole brain regions (18% and 10%, respectively).